Fluid-cooled internal combustion engines are cooled by a cooling fluid being circulated through the internal combustion engine and then usually also through a suitable radiator in heat-exchange relationship with the atmospheric air, with the cooling fluid being driven through the cooling fluid circuit by a pump. In this respect reference may be made to DE 100 58 374 A1 which provides that the cooling fluid is circulated through the engine by means of a pump driven by an electric motor, with the electric motor being controlled in dependence on the prevailing temperature of the cooling fluid. In that case semiconductor devices which serve to regulate operation of the electric pump motor and/or a radiator fan motor also perform the function of affording additional heating, with the semiconductor devices being operated in a lossy fashion when the internal combustion engine is in a cold-start condition, with the waste heat resulting therefrom being transferred to the cooling fluid. Particularly in the cold-start phase of the internal combustion engine, the cooling water can be quickly heated up without the need for an additional heating unit, as is known from EP 0 993 546 A1, with the consequence that the internal combustion engine is raised to its normal operating temperature of the order of magnitude of between 80° C. and 90° C. within a reduced period of time.